When using GuiXT features we are sometimes faced with the error message:
"0 capacity problem; resulting screen 76 bytes too large. No GuiXT modification"
What could be the reason?

In SAP GUI versions before SAP GUI 6.20, the interface between SAP GUI and GuiXT had a size limitation: screens with an internal size larger than 30000 could not be increased in size by GuiXT (e.g. by adding new elements). This usually happened on screens with large table controls (like VA01), and only if the window size was large, with several table lines on screen.

To avoid the problem, either use SAP GUI 6.20 where the size is no longer limited. Or, on SAP GUI 4.6d, delete some other elements, such as table columns that are not needed.
Example:

ColumnSize (All items,30) 0

ColumnSize (All items,31) 0

ColumnSize (All items,32) 0